1. The Field of the Invention
This invention relates to blood salvaging and autotransfusion apparatus and methods and, more particularly, to novel apparatus and methods for use during surgery for salvaging, washing, and concentrating blood so that healthy blood cells can be returned to a patient.
2. The Prior Art
During surgery, it is highly desirable that any blood and fluid which accumulate be transported away from the operative field. This is typically accomplished by means of a suction system which is used to aspirate blood and fluid from the areas of accumulation. In this way, the operative field is kept clean and unobscured so that successful completion of the surgical procedure will not be hindered.
During an operation, for example, as much as 250,000 cubic centimeters of blood may be aspirated from the operative field of a patient in the manner outlined above. As a result, unless this blood can be successfully returned to the patient, the aspirated blood must be replaced by blood from other sources. The process of salvaging a patient's blood from the operative field and then returning that blood to the patient is referred to generally herein as "autotransfusion."
When salvaging blood from an operative field, one, of course, recovers healthy blood cells, together with the associated blood plasma (the fluid portion of the blood). In addition, however, a number of undesirable substances are recovered along with and mixed together with the blood; the presence of the substances in the blood prevents the salvaged blood from being returned directly to the patient, thereby inhibiting autotransfusion.
Some of the undesirable substances recovered with the blood from an operative field are in the form of solid or particulate debris. Such debris may include the cell walls of red blood cells which have been damaged and ruptured, platelets, and leukocyte aggregates. In addition, the salvaged blood invariably contains tissue fragments and blood clots which result from the surgical procedures.
Besides such particulate debris, blood which is salvaged from an operative field has become contaminated with various other undesirable fluids. First, the cellular fluid which was inside of the now-ruptured blood cells is mixed together with the normal blood plasma. In addition, substantial amounts of other body fluids may also be present, especially when operating within the abdominal or chest cavities of a patient.
Moreover, the trauma incident to surgery and to the salvaging of blood may produce substances which do not normally exist within the body and which are then mixed together with the other substances recovered from the operative field. For example, a carbon atom may be knocked off of a carbon chain or a side radical may be eliminated from a carbon chain so as to produce substances which do not occur naturally. Such substances, which may be potentially harmful to the patient, thus become part of the salvaged blood mixture.
Because of the nature of the salvaged blood mixture, as described above, it will be readily appreciated that this blood mixture cannot safely be returned directly to the patient immediately after it is collected. Rather, it is necessary to first treat the salvaged blood mixture so as to remove at least a portion of the undesirable substances. Accordingly, those skilled in the art have developed apparatus which are designed to "wash" the blood prior to returning the blood to the patient.
When using the blood-washing devices known in the prior art, the salvaged blood mixture is first filtered so as to remove certain of the particulate debris. Thereafter, the blood mixture is then transferred to a centrifuge chamber. As the centrifuge chamber rotates, the blood cells separate from the blood plasma and the other salvaged fluids as a result of the difference in density between the blood cells and the plasma and other fluids.
Once the blood cells have been thus separated, a washing solution (such as, for example, a sterile saline solution), may be introduced into the centrifuge chamber so as to carry away the undesirable fluids together with the original blood plasma. At the completion of this procedure, the washed blood cells are then recombined with new blood plasma and returned to the patient.
Despite the overall effectiveness of the prior art blood washing devices, these devices suffer from a number of significant disadvantages. First, it will be readily appreciated that prior art blood-washing procedures, such as those outlined above, are quite slow. The prior art devices are, in fact, primarily directed for use by blood banks where batch processing is adequate and processing time is not an overriding concern.
Due to the large volumes of blood which are often collected from a patient during surgery, however, time becomes a crucial factor in the salvaging and washing of blood. Prior art devices have been found to be simply unresponsive to this time demand; and, as a result, when using the devices of the prior art during surgery for the purpose of autotransfusion, a patient's need for blood often becomes urgent to the point of emergency.
In addition, the prior art blood-washing devices are not readily adapted to continuous blood processing. As suggested from the discussion above, prior art devices generally involve batch processing of blood. Consequently, in spite of efforts to adapt the prior art devices to accept several batches of blood for simultaneous processing, prior art devices have not been capable of continuously washing and processing the blood during surgery.
Further, the prior art blood washing devices and methods cannot generally be interrupted once the processing has commenced. This is primarily due to the fact that the blood is not ready to be returned to the patient until it has been completely washed and then combined with new blood plasma. Consequently, when an emergency need arises, a patient must often be given blood from other sources or be forced, despite the inherent risk, to wait until the blood washing and processing can be fully completed.